It has been recognized for many years that the mammalian body requires for its nutrition relatively large amounts of fats, carbohydrates and proteins, and by contrast relatively small amounts of vitamins and minerals; lack of these latter classes of substances has been held to be accountable for the absence of general good health as well as the incidence of various specific bodily ailments. Vitamins and minerals are normally ingested or otherwise produced from the mammalian diet, but to a certain extent may also or alternatively be produced in the body. For various reasons which may be related to the source of supply or the manufacturing processes used, foods are sometimes lacking or deficient in vitamins and/or minerals, and even where vitamins are synthesized in the body, such a process may not produce the amount required. Over a period of time there has therefore grown up the use of food supplements, or nutritional compositions, to supply the ingredients of this nature required by the body, but which are either not produced therein in sufficient amounts, or are not supplied thereto by the regular diet of the subject in sufficient amounts.
Nutritional compositions are not at the present time, however, restricted merely to a content of vitamins and minerals, as the sole active ingredients. Other materials which are intermediate in metabolic processes and which it is thought may not be produced in sufficient amounts (at least in subjects with abnormal metabolism) may also be present in nutritional compositions. Examples of such other materials are unsaturated fatty acids, such as linoleic acid, gamma-linolenic acid, dihomogamma-linolenic acid arachidonic and eicosapentaenoic acids, as well as physiologically compatible derivatives thereof, such as salts, esters and amides of such acids, which may be metabolized in the body to prostaglandins. Prostaglandins are an important group of local hormones which act within the body tissues in which they are synthesized, in roles which are not entirely understood, though they may act at least to lower blood pressure, and to induce smooth muscle to contract.
Horrobin, in Med. Hypotheses 6: 469-486 (1980), has also proposed that a metabolic abnormality in the synthesis of certain prostaglandins is responsible for allowing an initial cancer cell to divide indefinitely, the abnormality being in particular, inhibition of the enzyme delta-6-desaturase which converts essential unsaturated fatty acids in normal cells to prostaglandins. He has also proposed pharmaceutical compositions (see e.g. EP 0037175 published Oct. 7, 1981 and prior patent applications referred to therein, the contents of which are to be regarded as incorporated herein by reference) comprising certain unsaturated fatty acids together with other ingredients which enhance formation in the body of essential prostaglandins and therefore bypass the metabolic abnormality referred to above.
In general, fatty acids in combined form are present in animal and vegetable fats and oils, but vegetable oils such as corn, cottonseed and soya oils contain in general a higher ratio of unsaturated to saturated acids, than do animal fats. A higher proportion of polyunsaturated fatty acids (such as linoleic and linolenic acids) in the diet apparently tends to reduce the incidence of heart disease, although whether this is due to a positive effect of the polyunsaturated compounds themselves, rather than to an intake of a correspondingly lower proportion of saturated compounds (and of cholesterol which is also present in animal fats), or to a lower fat intake overall, remains uncertain.
Senile dementia of Alzheimer's type (more commonly known as "Alzheimer's disease") appears to be the most widespread neuropsychiatric disease and is becoming increasingly prevalent with the general aging of the population. It is not, however, confined to the elderly, as this term is generally understood. To the best of the inventor's knowledge, no satisfactory treatment for this type of dementia or for related dementias has yet been evolved.
The term "epilepsy" denotes a group of central nervous system disorders characterized by transitory episodes of abnormal motor, sensory, autonomic or psychic phenomena, and are almost always correlated with abnormal and excessive discharges in the encephalogram. Most known useful antiepileptic agents are either barbiturates or are structurally related thereto, or are benzodiazepines, dibenzoazepines, or lipids or lipid-like compounds containing phosphorus and/or nitrogen. Valproic acid (Pr.sub.2 CHCOOH) and its derivatives are also useful in this respect. However, to the inventor's knowledge, it has not hitherto been proposed to use polyunsaturated unbranched long-chain carboxylic acids, containing only C, H and O, as antiepileptic compounds.
It has now been surprisingly found in accordance with the present invention, that a combination of two naturally occurring polyunsaturated acids within a certain range of proportions, produces certain beneficial effects in the human and animal body, including memory enhancement, analgesia, sleep regulation and inhibition of the symptoms of senility; and may also be used in a method of treatment for Alzheimer's disease and related dementias, and epilepsy, which method relieves at least certain symptoms of such diseases.
Experiments carried out by the inventor support the belief that it is the combination of these acids themselves in particular proportions which is the active factor in producing the beneficial and therapeutic effects just referred to; there is no evidence at present that such effects are connected with the metabolization of these acids to other substances.
It is particularly to be noted that the beneficial and therapeutic effects of the combination of the two specified acids (or their derivatives) may be adversely effected by the presence of an oily carrier or diluent which comprises at least one member of the group consisting of C.sub.8-18 saturated fatty acids, oleic acid and derivatives of these acids, and the invention thus excludes the use of such diluents or carriers. As persons skilled in the art will be aware, the use of natural oil diluents and carriers of vegetable or animal origin is accordingly excluded from the scope of the invention.